The present embodiments relate to a magnetic resonance device with a switching matrix unit, a method for optimization of a preliminary pulse sequence, and a computer program product.
Magnetic resonance tomography (MRT) is a known technique for creating images of the inside of the body of an examination object. A basic magnetic field is overlaid in a magnetic resonance device with rapidly switched gradient fields, which are created by a gradient system of the magnetic resonance device. Radio-frequency excitation pulses are irradiated into the examination object by a radio-frequency antenna unit of the magnetic resonance device to trigger magnetic resonance signals are shortened, and the triggered magnetic resonance signals are recorded, based on which magnetic resonance images are created. In such cases, the recorded magnetic resonance signals are demodulated phase-sensitively and converted by sampling and by analog-digital conversion into complex-number values, which are stored in a k-space matrix, from which a magnetic resonance image is able to be reconstructed by a multi-dimensional Fourier transformation.
One of the uses of the aforesaid gradient fields in such cases is for local encoding. This provides that the gradient fields have the task of making the contributions of individual voxels of a region of the examination object to be imaged distinguishable. In such cases, the gradient fields are used in connection with the radio-frequency signals for selective excitation of a predeterminable region of the examination object (e.g., a slice, and/or for spatial encoding within an excited region; a slice or a larger volume).
The gradient system of currently usual magnetic resonance devices includes three gradient coils, each for one spatial direction, which each create a spatially linear gradient field. In accordance with more recent ideas from research, non-linear gradient fields are also used (e.g., by using three non-linear gradient fields or by overlaying three linear gradient fields with further non-linear gradient fields). The result of this may be that there is a need for additional gradient coils (e.g., for creating the non-linear gradient fields as well as the currently usual three gradient coils).
Nowadays the gradient coils are typically each connected to a gradient amplifier, which also often have equal power. Thus N gradient coil amplifiers are needed for N gradient coils, regardless of whether the system involved is a conventional system with three or possibly a research system with more than three gradient coils.